The present invention relates to a switch device for controlling supply of a power source voltage to a load.
Mechanical switches or semiconductor switches such as thyristors and triacs are used as means for opening and closing an electric circuit including a power source and a load. If the load is inductive in such an electric circuit, then a surge current which is more than ten times a steady-state current will flow upon closure of the circuit. When such a surge current flows, a circuit breaker interposed between the power source and the load will operate. This means that the circuit breaker must be reset every time the electric circuit is closed.
A zero-volt switch for power control is known. A zero-volt switch of this type has a phase detector for detecting a zero volt point of an AC voltage, and a trigger circuit for turning on a semiconductor switch at a timing that the AC voltage crosses the zero-volt point. Even if the zero-volt switch of this type is used for power control for an inductive load with a core, the surge current cannot be suppressed due to the inductance of the load.